Body Mass Index and Waist Hip Ratio

By Dr Utpal Sharma

Assistant ProfessorDept Of Community Medicine

Sikkim Manipal Institute of Medical Sciences

IntroductionBody Mass Index (BMI) is the latest tool to assess the

amount of body fatness in a person.

It is a calculation using a person’s height and weight.

Health professionals use BMI to determine if one is underweight, a healthy weight, overweight or obese.

BMI can provide an indication of weight categories that could lead to future health problems.

BMI levels are interpreted differently for adults and children so different BMI calculators are used.

How is BMI used as a Measure of Health?

BMI is used to screen for weight problems that may lead to future health problems

For most people BMI is a reliable indicator of body fatness

The higher the BMI number, the more body fat a person has.

Is BMI always a reliable indicator of Body Fatness?

Although BMI is a reliable indicator of body fatness for most people there is an exception:

Athletes: physically fit, may have a high BMI due to a lot of muscle mass but not due to a high level of body fatness.

How do you calculate BMI for adults

BMI can be calculated using the formula:

BMI calculator: an easier method is to use a BMI calculator.

The adult BMI calculator is used to determine the BMI for people 20 years of age and over.

How to interpret BMI levels for adults?

Classification BMI(kg/m2)Underweight <18.50     Severe thinness <16.00     Moderate thinness 16.00 - 16.99     Mild thinness 17.00 - 18.49

Normal range 18.50 - 24.99

Overweight ≥25.00     Pre-obese 25.00 - 29.99     Obese ≥30.00          Obese class I 30.00 - 34.99          Obese class II 35.00 - 39.99          Obese class III ≥40.00

Source: Adapted from WHO, 1995, WHO, 2000 and WHO 2004

BMI calculation

How to interpret BMI levels for children?

For those over 2 years to 20 years of age, calculating and interpreting BMI levels is different than for an adult.

The BMI is calculated from the child’s weight and height, age and sex.

For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

Cont….

BMI percentile: a percentile ranking is also determined.

It is this percentile that is used to evaluate a child’s weight status.

Like adults, BMI is used to determine if a child is underweight, a healthy weight, overweight or obese.

The CDC BMI-for-age growth charts

BMI Table for ChildrenOnce a BMI percentile is calculated for a child,

then the table below is used:

Weight Status Category

Percentile Range

Underweight Less than the 5th percentile

Healthy weight5th percentile to less than the

85th percentile

Overweight85th to less than the 95th

percentile

ObeseEqual to or greater than the

95th percentile

Waist hip ratio

Introduction The WHR has been used as an

Indicator or measure of the health of a person, and….. Risk of developing serious health conditions

WHR is used as a measurement of obesity….

……which in turn is a possible indicator of other more serious health conditions.

WHR has been shown to be a better predictor of cardiovascular disease than waist circumference and body-mass index

Regional Fat Deposition

Abdominal body fat poses greater health risks than fat stored in other areas

Males store more fat centrally and have increased health risks associated with body fatness Higher health risk Lower health risk

Male (apple) Female (pear)

Types of obesity

How to measure WHR?

According to WHO the waist circumference should be measured at…..

…….the midpoint between the lower margin of the last palpable rib and the top of the iliac crest.

Hip circumference should be measured around…..

………. the widest portion of the buttocks, with the tape parallel to the floor. 

WHR has been found to be a more efficient predictor of mortality in older people than waist circumference or BMI

Cont….

WOMENMEN

High RiskModerate RiskLow Risk

> 1.0 > .85.90 -1.0 .80-.85

HEALTH RISK

< .90 < .80

Waist to Hip Ratio (WHR)

Waist to Hip Ratio is an effective way to examine regional fat distribution.

WHR is not considered to be as valid for Children….. People who are under five feet tall or…..Who have a body mass index (BMI) of 35 or above.